1. Field of the Invention
The present invention relates to name retrieval methods and name retrieval apparatuses, and particularly relates to a name retrieval method and a name retrieval apparatus which are suitable for performing retrieval by successively performing search refinement every time a character is input and displaying a result of the retrieval.
2. Description of the Related Art
Conventionally, a navigation apparatus enables retrieval of a retrieval-target name such as an address name or a POI (Points of Interest) name. The apparatus provides for a character input to retrieve a destination from a database that stores character string data corresponding to a retrieval-target name.
Furthermore, at a time of such name retrieval, conventionally, fuzzy matching may be used to retrieve a retrieval-target name that includes a symbol such as a hyphen or a comma without inputting the symbol. The retrieval is performed by replacing a special character (such as an alphabet with an umlaut mark or an alphabet with a ring) with a normal alphabet. However, in other cases, except for such exceptions, a retrieval-target name is generally retrieved only when a character string that is input is the same as that representing the retrieval-target name stored in the database.
As an example, in Arabic-speaking countries, when a plurality of specific characters are sequentially arranged in a certain order, a series of the characters can be united with one another so as to be represented by a ligature. However, in a navigation system that supports Arabic, different character codes are assigned to a certain ligature and a series of characters corresponding to the ligature (obtained by cancelling the ligature unit).
For example, three different character codes are assigned to a ligature “Lam alif” (represented by alphabetical characters for convenience sake) and characters “Lam” and “alif” that correspond to the ligature “Lam alif” (for example, Lam: 0644, alif: 0627, and Lam alif: FEFB).
If only the character “Lam” is input when a retrieval-object name is to be retrieved, a retrieval-target name is not detected that includes “Lam alif” which has the character code different from that of “Lam”. Similarly, if the ligature “Lam alif” is input, a retrieval-target name is not detected that includes “Lam+alif” (series of two characters) which has the character code different from that of the ligature “Lam alif”.
Retrieval leakage of a retrieval-target name depends on not only a character code, but also on an arbitrary determination as to whether the series of characters is used as a ligature (hereinafter referred to as arbitrary property of a ligature).
Specifically, in a database included in a navigation apparatus, although original data is compiled by a compiler, a creator of the original data determines whether retrieval-target names to be stored in the original data which may be represented by a ligature are stored using a ligature. However, in many cases, the determination is made by following a notation system of local signboards. Then, according to the arbitrary property of a ligature, the local signboards may use character strings using ligatures or may use character strings using series of a plurality of characters corresponding to the ligatures. Therefore, in the database, retrieval-target names represented by a ligature corresponding to a series of a plurality of characters and retrieval-target names represented by a series of a plurality of characters are often mixed. This encourages the retrieval leakage of retrieval-target names.
In Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2002-507289, a technique of identifying and displaying an alternative glyph (ligature) in text has been proposed. In such a technique, display is performed taking a ligature into consideration.
However, although taking a ligature into consideration only when display is performed, the technique disclosed in Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2002-507289 does not support name retrieval taking the arbitrary property of a ligature into consideration.